Transformer Fault in a PSU?

[Rob Jarratt]

> -----Original Message-----
> From: cctalk <cctalk-bounces at classiccmp.org> On Behalf Of Jon Elson via
> cctalk
> Sent: 13 January 2020 04:49
> To: Stefan Skoglund <stefan.skoglund at agj.net>; General at ezwind.net;
> Discussion at ezwind.net:On-Topic and Off-Topic Posts
> <cctalk at classiccmp.org>
> Subject: Re: Transformer Fault in a PSU?
> 
> On 01/12/2020 10:34 PM, Stefan Skoglund via cctalk wrote:
> > sön 2020-01-12 klockan 21:10 +0000 skrev Rob Jarratt via cctalk:
> >> The PSU in my VAXmate failed recently and I think I have found a
> >> problem with one of the windings on the transformer not ringing when
> >> I test it with a ringing tester. The technical description of the
> >> VAXmate says that one winding is operated in flyback mode and I
> >> wonder if that has any bearing on the ringing test. Also, one of the
> >> pins appears not to be connected to anything else, so possibly a
> >> broken (melted?) wire.
> >>
> >>
> >>
> >> Can anyone help with the following questions:
> > The transformer is basically only intended to provide AC at a specific
> > voltage while preventing surges and noise from the utility to create
> > havoc.
> > What voltage is it specified to provide ? If so, can it be replaced
> > with maybe a new AC to AC device ?
> >
> >
> The transformer Rod describes and provided schematic for is
> part of a switching power supply,
> and not a 50/60 Hz mains transformer.  From the picture, it
> is almost certainly a ferrite core
> transformer running at 25+ KHz.
> 


According to the Technical Description the NE555 is arranged to oscillate at 100KHz, and I did indeed measure that frequency, when it oscillated.

Regards

Rob